The present invention relates to a polishing apparatus for polishing a substrate, e.g. a semiconductor wafer, in which a fixed abrasive member or an abrasive polishing disc is employed. More particularly, the present invention relates to an arrangement of a dressing member used for dressing (regenerating) the fixed abrasive member, and relates also to a method of dressing the abrasive disc.
With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit wiring patterns have become increasingly fine. To produce such fine circuit wiring patterns, it is necessary for the surface of a substrate on which such patterns are formed to be exceptionally flat. To this end, a so-called chemical/mechanical polisher (CMP) has been widely employed. A chemical/mechanical polisher (CMP) comprises a turntable provided with a polishing cloth (pad) bonded thereto and a substrate carrier. The substrate carrier is designed to hold a semiconductor substrate to be polished and bring it into contact with the polishing cloth. During a polishing operation, a chemical polishing liquid (slurry) containing abrasive particles is supplied to the polishing pad, and a surface of a substrate subject to a polishing operation is polished until it becomes flat and specular.
However, in conventional chemical/mechanical polishers (CMPs), there is a tendency for a xe2x80x9cpattern dependencyxe2x80x9d problem to arise. Namely, an area on which a wiring pattern having small pattern pitches is provided is subject to a relatively high degree of polishing, while an area provided with a wiring pattern having a large pattern of pitches is subject to a relatively low degree of polishing, which creates inconsistencies in the form of undulations on the polished surface of the semiconductor substrate. As a result, it is difficult to obtain a polished surface having the requisite degree of flatness. Further, in a chemical/mechanical polisher (CMP) employing a polishing pad, when a substrate on which a circuit pattern has been formed and thus there exist raised portions and recessed portions on the surface of the substrate, not only are the raised portions polished, but also the recessed portions. This makes it impossible to cause the polisher to realize a so-called self-stop function whereby the polisher substantially stops its polishing function or the polishing rate becomes nearly zero when the raised portions have been sufficiently polished to thereby attain a high degree of flatness of the substrate surface.
As an alternative to a conventional CMP, research has been conducted with a view to polishing semiconductor wafers or the like by means of a fixed abrasive member comprising abrasive particles of, for example, cerium oxide (CeO2) bonded by a binder such as a phenolic resin. As compared with a conventional chemical/mechanical polishing device wherein a polishing pad is utilized, use of a fixed abrasive member is advantageous in that it is relatively easy to attain the requisite degree of flatness of a polished surface since recessed portions formed in a circuit pattern area are not subject to polishing. In addition, if fixed abrasive members are used in conjunction with particular kinds of abrasive particles, it is possible to realize the so-called self stop noted above. Furthermore, in utilizing a fixed abrasive member no polishing slurry is required, which is environmentally advantageous.
However, in a semiconductor wafer polishing process using a fixed abrasive member, the polishing efficiency, although high just after dressing of the fixed abrasive member, gradually deteriorates. Accordingly, in order to maintain efficient and effective polishing, it is necessary to dress or condition the fixed abrasive member before each polishing operation by using, for example, a dressing member including a number of diamond particles bound to its surface so as to generate a sufficient quantity of free or loose abrasive particles. However, carrying out dressing of the fixed abrasive member before each polishing operation is inefficient and has a negative effect on productivity.
Furthermore, using a dressing member provided with diamond particles to regenerate the surface of a rigid polishing member involves a problem in that the diamond particles are liable to become detached and scratch or otherwise damage the surface of a substrate to be polished.
In view of the above-described circumstances, an object of the present invention is to provide a substrate polishing apparatus using a fixed abrasive member which is free from the problem that diamond particles may detached from the abrasive member and fall onto the polishing surface, and which is capable of stably freeing abrasive particles from the polishing surface of the abrasive member, thereby allowing polishing to be performed at a stabilized polishing rate, and also to provide an abrasive member dressing method.
Another object of the present invention is to provide a dressing apparatus or method capable of appropriately freeing abrasive particles from an abrasive member and thus increasing the lifetime of the abrasive member.
In dressing of the fixed abrasive member, the dressing member surface is slidingly engaged with the polishing surface of the abrasive member, thereby freeing a sufficient amount of abrasive particles from the abrasive member. Thus, in accordance with this invention, it becomes possible to eliminate the likelihood of detachment of diamond particles, such as is likely to occur in using a conventional diamond dressing member, and accordingly it is possible to prevent scratches or other damage from being created on a surface of a substrate to be polished. As the dressing member, it is preferable to use a ceramic dressing member consisting essentially of SiC or diamond-like carbon.
According to another aspect of the present invention, there is provided a substrate polishing apparatus comprising a fixed abrasive member having a polishing surface, the polishing surface being slidingly engaged with a substrate to be polished, and a dressing member having a dressing surface adapted to be slidingly engaged with the polishing surface of the fixed abrasive member for dressing the polishing surface of the abrasive member. The dressing member is in the shape of a rod extending from a center of the abrasive member to an outer periphery thereof. Thus, the rod-shaped dressing member and the surface to be dressed of the abrasive member come into linear contact with each other uniformly over the entire radius of the abrasive member. This enables the dressing member to dress the abrasive member uniformly.
According to another aspect of the present invention, there is provided a substrate polishing apparatus comprising a substrate carrier for carrying a substrate, a fixed abrasive member having a polishing surface, the polishing surface being slidingly engaged with a substrate carried by the substrate carrier for effecting polishing, and a dressing member having a dressing surface adapted to be slidingly engaged with the polishing surface of the fixed abrasive member for dressing the polishing surface. The dressing member is in the shape of a ring and provided on the substrate carrier in such a manner that the dressing member is placed around the substrate with the dressing surface being set flush with a surface of the substrate to be polished. In this polishing apparatus, abrasive particles are effectively and appropriately liberated from the abrasive member while effecting polishing.
According to another aspect of the present invention, there is provided a method for dressing a polishing surface of a fixed abrasive disc in a substrate polishing apparatus wherein a substrate is brought into engagement with the polishing surface of the fixed abrasive disc rotating about its axis while rotating the substrate. The method comprises the steps of preparing a dressing member having a dressing surface, bringing the dressing surface of the dressing member into engagement with the polishing surface of the rotating fixed abrasive disc and controlling the ratio of the number of revolutions of the dressing member to a number of revolutions of the fixed abrasive disc so as to adjust the dressing conditions. In such a way, the surface configuration of the abrasive disc can be adjusted to the desired configuration, whereby even when the polishing surface of the abrasive disc is not flat, the substrate surface can be polished to the requisite degree of flatness.
Preferably, the dressing surface of the dressing member is engaged with the polishing surface of the rigid rotating abrasive disc under a pressure of not more than 30 g/cm2 so as to improve the stability of the polishing rate and to increase the lifetime of the abrasive disc.
According to a further aspect of the present invention, there is provided a method for dressing a polishing surface of a fixed abrasive member used in a substrate polishing process wherein a substrate is brought into engagement with the polishing surface of the fixed abrasive member and subjected to a relative sliding motion therebetween, thereby causing the substrate to be polished. The method comprises supplying the polishing surface of the fixed abrasive member with a liquid capable of dissolving a binder binding abrasive particles and forming the polishing surface of the fixed abrasive member to promote the generation of freed abrasive particles. In this method, it is not necessary to employ a dressing member.
According to another aspect of the present invention, there is provided a method for dressing a polishing surface of a fixed abrasive member used in a substrate polishing process wherein a substrate is brought into engagement with the polishing surface of the fixed abrasive member and subjected to a relative sliding motion therebetween, thereby causing the substrate to be polished. The method comprises passing an electric current through the fixed abrasive member, thereby breaking bonds of a binder binding abrasive particles of the fixed abrasive member to promote the generation of freed abrasive particles.
According to another aspect of the present invention, there is provided a method for dressing a polishing surface of a fixed abrasive member used in a substrate polishing process wherein a substrate is brought into engagement with the polishing surface of the fixed abrasive member and subjected to a relative sliding motion therebetween, thereby causing the substrate to be polished. The method comprises the steps of preparing the fixed abrasive member containing photocatalyst in the polishing surface made of abrasive particles bound by a binder and irradiating the polishing surface of the fixed abrasive member, thereby breaking bond of the binder in the polishing surface to promote the generation of freed abrasive particles.